The present invention concerns increasing the temperature at which an electronic device containing a digital processor may operate without causing a temperature of the processor to exceed the processor manufacturer's temperature specification.
Essentially all electronic devices are specified to operate within a certain temperature range. Operation outside that temperature range can impair the performance of the electronic device or can even cause irreparable harm to the device. The disclosed invention describes a method to increase the maximum allowable operation temperature of an electronic device, specifically a device that contains a digital processor. Digital processors find application today in a wide variety of products. The term “electronic device” as used herein includes electronic equipment including computers, desktop computers, portable or laptop computers, video or audio systems, control systems, switches, relays, communications devices, power protection systems, input-output modules, power supply modules or power supplies, adapters, suppressors, and all sorts of consumer and industrial electrical products, whether they are stand-alone, rack-mounted, or otherwise configured in their packaging. The term is not limited to just industrial products but also comprehends consumer electronics and vehicular applications. The invention is applicable to electronic devices containing a digital processor.
For example, a processor that is currently in use is a Transmeta Crusoe TM5700. The maximum junction temperature Tj for that processor specified by its manufacturer is 100 degrees C. In specifying a maximum allowable temperature for the electronic device containing the processor, the designer must take into account the several temperature drops involved in the heat transfer from the component to outside air, and must ensure that the sum of these drops does not cause the semiconductor component to exceed its specified maximum junction temperature rating. Users of electronic devices are usually interested in the maximum allowable temperature of the air surrounding the electronic device. Some users desire a higher allowable temperature. This may occur in, for example, an application where heat builds up from either internal sources or environmental sources. Just one example would be within a power station or relay station. There are many other applications where temperature is a factor that must be considered in the design of an electronic device that is to operate in such an environment. For the designer of the electronic device to tolerate an increased maximum allowable temperature of the air surrounding the device, he must decrease the sum of all of the remaining temperature drops to keep the overall sum at a relatively constant level.
The temperature range of a device containing electronic components takes into account several temperatures and temperature differentials (“drops”) as contemplated by FIG. 1, which shows a semiconductor integrated circuit 10 having a representative junction 12 within it. Integrated circuit 10 is mounted in a case or package 14. Package 14 is mounted to or on a printed circuit board 16. The printed circuit board 16 is connected to a device chassis 18. The temperature of the junction 12 is affected by the temperatures of the case 14, the inside air temperature, the device chassis temperature, the outside air temperature, and a zero temperature reference. Hence, the temperature of junction 12 is a function of: (a) the drop 22 from junction 12 to the integrated circuit case 14, (b) the temperature drop 24 from the case 14 to the chassis inside air temperature, (c) the temperature drop 26 from the air surrounding the component (chassis inside air temperature) to the chassis 18, (d) the temperature drop 30 from chassis 18 to the outside air 32 surrounding the electrical device, and (e) the temperature drop 34 from the outside air 32 to the absolute zero temperature reference. The sum of all of these temperature drops determines the junction temperature of the semiconductor device 10. The manufacturer of the semiconductor component 10 specifies the maximum junction temperature of the component for safe, reliable operation of the component.
In rating the maximum allowable temperature for the electronic device containing the semiconductor component 10, the designer of the electronic device must take into account all of these temperature differences and ensure that their sum does not exceed the rating of the semiconductor component. Users of electronic devices are usually interested in the maximum allowable temperature of the air surrounding the electronic device. Some users desire a higher allowable temperature. For the designer of the electronic device to increase the maximum allowable temperature of the air surrounding the device, they must decrease the sum of all of the remaining temperature drops to keep the overall sum from exceeding the maximum rating of the semiconductor component. That is, if the difference between the zero temperature reference and the outside air temperature is increased, then to avoid an increase of the junction temperature, one must decrease one or more of the temperature differentials between the outside air temperature and the junction temperature. With reference to the Transmeta Crusoe TM5700 processor mentioned above, for example, the manufacturer of the electronic device employing that processor will want to determine the maximum ambient temperature that the device can sustain or tolerate without increasing the junction temperature Tj in the processor beyond the 100 degrees C. rating.
Well known ways of decreasing some of the remaining temperature drops include painting the chassis black to help it radiate heat more efficiently (which reduces the chassis to outside air temperature drop), putting cooling fins on the chassis to help convection remove heat from the chassis more efficiently (which also reduces the chassis to outside air temperature drop), putting a fan on or inside the device (which primarily helps reduce the case to inside air temperature drop, but can also reduce the inside air to device chassis temperature drop), putting cooling slots in the chassis (which helps reduce the inside air temperature to outside air temperature drop), connecting the semiconductor package directly to the chassis with a material that has a low thermal resistance (which helps reduce the semiconductor package to device chassis temperature drop), and other approaches.
Many prior art approaches to temperature control involve integrating a temperature sensor so that high temperatures can be detected and dealt with. For example, Hitachi introduced a temperature sensor into its Ultrastar server disk drives so that high temperature conditions are reported to the host system using the Self-Monitoring Analysis and Reporting Technology (SMART) standard. If the computer system is alerted to temperature problems, the user or system administrator can take action. See “Hitachi's Drive Temperature Indicator Processor (Drive-TIP) Helps Ensure High Driver Liability,” by Gary Herbst available on an Hitachi web site (http://www.hitachigst.com/hdd/technolo/drivetemp/drivetemp.htm). Herbst mentions that the cooling capacity can be varied depending on component needs and, illustratively, fan speed can be controlled based on temperature within the system.
It is also known to regulate microprocessors in response to sensed temperature. For example, U.S. Pat. No. 6,119,241 entitled “Self Regulating Temperature/Performance/Voltage Scheme for Micros (X86)” to Michail et al. (IBM) optimizes processor performance by switching to an accelerated clock and voltage state when a temperature sensed in the processor is under an optimum temperature. Also, it exercises utilization control over the processor functional units when the temperature exceeds the optimal temperature, and switches to normal clock states and normal voltages at other temperatures.
The preferred embodiment of the present invention, on the other hand, is concerned with enabling an electronic device having a digital processor to operate at an elevated ambient temperature, that is, elevated beyond the temperature at which it could normally operate. It achieves this by controlling the heat generated by the electronic device itself. This is achieved preferably by determining a limit relating to processor performance, arranging the operation of the data processor generally to fall below the determined limit, detecting the processor utilization during operation, and preferably performing a notification if the processor utilization exceeds the determined limit.